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The 4‐cysteine zinc‐finger motif of the RNA polymerase regulator DksA serves as a thiol switch for sensing oxidative and nitrosative stress
Author(s) -
Henard Calvin A.,
Tapscott Timothy,
Crawford Matthew A.,
Husain Maroof,
Doulias PaschalisThomas,
Porwollik Steffen,
Liu Lin,
McClelland Michael,
Ischiropoulos Harry,
VázquezTorres Andrés
Publication year - 2014
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.12498
Subject(s) - zinc finger , cysteine , biology , regulator , thiol , oxidative phosphorylation , biochemistry , oxidative stress , rna , rna polymerase , zinc , microbiology and biotechnology , enzyme , gene , chemistry , transcription factor , organic chemistry
Summary We show that thiols in the 4‐cysteine zinc‐finger motif of DksA , an RNA polymerase accessory protein known to regulate the stringent response, sense oxidative and nitrosative stress. Hydrogen peroxide‐ or nitric oxide ( NO )‐mediated modifications of thiols in the DksA 4‐cysteine zinc‐finger motif release the metal cofactor and drive reversible changes in the α‐helicity of the protein. Wild‐type and relAspoT mutant S almonella , but not isogenic dksA ‐deficient bacteria, experience the downregulation of r‐protein and amino acid transport expression after NO treatment, suggesting that DksA can regulate gene expression in response to NO congeners independently of the ppGpp alarmone. Oxidative stress enhances the DksA ‐dependent repression of rpsM , while preventing the activation of livJ and hisG gene transcription that is supported by reduced, zinc‐bound DksA . The inhibitory effects of oxidized DksA on transcription are reversible with dithiothreitol. Our investigations indicate that sensing of reactive species by DksA redox active thiols fine‐tunes the expression of translational machinery and amino acid assimilation and biosynthesis in accord with the metabolic stress imposed by oxidative and nitrosative stress. Given the conservation of Cys 114 , and neighbouring hydrophobic and charged amino acids in DksA orthologues, phylogenetically diverse microorganisms may use the DksA thiol switch to regulate transcriptional responses to oxidative and nitrosative stress.